• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.2
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• pp.236-244
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• 2005

In this study, we introduce a new topology of Fuzzy Polynomial Neural Networks(FPNN) that is based on fuzzy relation and evolutionally optimized Multi-Layer Perceptron, discuss a comprehensive design methodology and carry out a series of numeric experiments. The construction of the evolutionally optimized FPNN(EFPNN) exploits fundamental technologies of Computational Intelligence. The architecture of the resulting EFPNN results from a synergistic usage of the genetic optimization-driven hybrid system generated by combining rule-based Fuzzy Neural Networks(FNN) with polynomial neural networks(PNN). FNN contributes to the formation of the premise part of the overall rule-based structure of the EFPNN. The consequence part of the EFPNN is designed using PNN. As the consequence part of the EFPNN, the development of the genetically optimized PNN(gPNN) dwells on two general optimization mechanism: the structural optimization is realized via GAs whereas in case of the parametric optimization we proceed with a standard least square method-based learning. To evaluate the performance of the EFPNN, the models are experimented with the use of several representative numerical examples. A comparative analysis shows that the proposed EFPNN are models with higher accuracy as well as more superb predictive capability than other intelligent models presented previously.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.611-617
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• 2010

A complex system involves a large number of design variables, and its operation is non-linear. To explore the characteristics in its design space, a Kriging meta-model can be utilized; this model has replaced expensive computational analysis that was performed in traditional parametric design optimization. In this study, a Kriging meta-model with a computational orthogonal array for the design of experiments was developed to optimize the fatigue life of a turbine blade whose behavior under cyclic rotational loads is significantly non-linear. The results not only show that the maximum fatigue life is improved but also indicate that the accuracy of computational analysis is achieved. In addition, the robustness of the results obtained by six-sigma optimization can be verified by comparison with the results obtained by performing Monte Carlo simulations.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.3
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• pp.386-401
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• 2011

Mathematical models for various steps in coal gasification reactions were developed and applied to investigate the effects of operation parameters on dynamic behavior of gasification process. Chemical reactions considered in these models were pyrolysis, volatile combustion, water shift reaction, steam-methane reformation, and char gasification. Kinetics of heterogeneous reactions between char and gaseous agents was based on Random pore model. Momentum balance and Stokes' law were used to estimate the residence time of solid particles (char) in an up-flow reactor. The effects of operation parameters on syngas composition, reaction temperature, carbon conversion were verified. Parameters considered here for this purpose were $O_2$-to-coal mass ratio, pressure of reactor, composition of coal, diameter of char particle. On the basis of these parametric studies some quantitative parameter-response relationships were established from both dynamic and steady-state point of view. Without depending on steady state approximation, the present model can describe both transient and long-time limit behavior of the gasification system and accordingly serve as a proto-type dynamic simulator of coal gasification process. Incorporation of heat transfer through heterogenous boundaries, slag formation and steam generation is under progress and additional refinement of mathematical models to reflect the actual design of commercial gasifiers will be made in the near futureK.

• Wind and Structures
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• v.9 no.4
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• pp.271-296
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• 2006

The frequency of a traditional tuned liquid column damper (TLCD) depends solely on the length of liquid column, which imposes certain restrictions on its application to long span cable-stayed bridges during construction. The configuration of a cable-stayed bridge varies from different construction stages and so do its natural frequencies. It is thus difficult to apply TLCD with a fixed configuration to the bridge during construction or it is not economical to design a series of TLCD with different liquid lengths to suit for various construction stages. Semi-active tuned liquid column damper (SATLCD) with adaptive frequency tuning capacity is studied in this paper for buffeting response control of a long span cable-stayed bridge during construction. The frequency of SATLCD can be adjusted by active control of air pressures inside the air chamber at the two ends of the container. The performance of SATLCD for suppressing combined lateral and torsional vibration of a real long span cable-stayed bridge during construction stage is numerically investigated using a finite element-based approach. The finite element model of SATLCD is also developed and incorporated into the finite element model of the bridge for predicting buffeting response of the coupled SATLCD-bridge system in the time domain. The investigations show that with a fixed container configuration, the SATLCD with adaptive frequency tuning can effectively reduce buffeting response of the bridge during various construction stages.

• Plant Journal
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• v.15 no.4
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• pp.43-51
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• 2019

The stress concentration of the integral welded attachments (IWA) often used to support piping system has been a big issue because it induces local stresses in piping. The method to evaluate local stresses associated with attachments on elbows has been suggested in EPRI TR-107453. However, there are limitations regarding specific parameters range in order to use correlation equation. In this paper, parametric study based on piping elbow size and attachment dimension was performed utilizing finite element analysis (FEA) to evaluate the secondary stress indices of hollow circular cross section welded attachments on piping elbows with the extended parameters range. The results of the FEA were used to develop correlation formulas for calculating secondary stress indices. The empirical equations in this study are suggested as an alternative evaluation method of EPRI TR-107453 by extending parameters range.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.91-99
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• 2017

The parametric study was performed for performance enhancement of wave energy converter(WEC) using a submerged pendulum plate. The wave exciting moment and hydrodynamic moment were obtained by means of eigenfunction expansion method based on the linear potential theory, and then the roll response of a pendulum plate and time averaged extracted power were investigated. The optimal PTO damping coefficient was suggested to give optimal extracted power. The peak value of optimal extracted power occurs at the resonant frequency. The resonant peak and it's width increase, as the height and thickness of a pendulum plate increase. The mooring line installed at the end of the pendulum plate is effective for extracting wave energy because it can not only induce the resonance with the waves of the installation site but also increase the restoring moment in case of PTO-on. The WEC using a rolling pendulum plate suitable for the shallow water acts as breakwater as well as energy extraction device.

• Journal of the Korean Society for Library and Information Science
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• v.42 no.2
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• pp.371-392
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• 2008

The books and circulation-related data in the Online Public Access Catalog System of the H-Public library were collected and analyzed in this paper. The methods which may be applied to the Customer Relationship Management in a public library based on the results were also suggested here. Collected data were 57,927 bibliographic data of books, 11,871 patron data and 27,145 circulation records. The type of collections. circulation frequencies, total number of circulated books, publication year, and use factor as relation factor from the analyzed data of circulation records were extracted. They were also analyzed, and verified by various statistical methods such as correlation coefficient, non-parametric method, etc.

• The KIPS Transactions:PartB
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• v.17B no.6
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• pp.405-412
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• 2010

Previous background generation techniques showed bad performance in complex environments since they used only temporal contexts. To overcome this problem, in this paper, we propose a new background generation method which incorporates spatial as well as temporal contexts of the image. This enabled us to obtain 'clean' background image with no moving objects. In our proposed method, first we divided the sampled frame into m*n blocks in the video sequence and classified each block as either static or non-static. For blocks which are classified as non-static, we used MRF framework to model them in temporal and spatial contexts. MRF framework provides a convenient and consistent way of modeling context-dependent entities such as image pixels and correlated features. Experimental results show that our proposed method is more efficient than the traditional one.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.1-10
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• 2004

A study on the evaluation of proper spacing and required flexural rigidity of cross beams in composite two I-section steel girder bridges without a lateral and sway bracing system was performed. Specifically, a 2-lane, 40-m simple span bridge and a 3-span continuous (40+50+10m) bridge were designed, and structural analyses under dead load before and after composite, live, wind, and seismic loads were performed using spacing and flexural rigidity or cross beams as parameters. Through parametric analysis, the effect on the stresses due to the combination of loads and live load distribution was investigated. In addition. material and geometric nonlinear analyses under dead load before composite were performed to evaluate the lateral buckling strength of the steel girders and cross beam. Based on the results or such analyses, the proper spacing and flexural rigidity of cross beams at intermediate points and supports were proposed.

• Earthquakes and Structures
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• v.11 no.3
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• pp.517-538
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• 2016

This paper presents a probabilistic fragility analysis for two groups of bridges: simply supported and integral bridges. Comparisons are based on the seismic fragility of the bridges subjected to accelerograms of two seismic sources. Three-dimensional finite-element models of the bridges were created for each set of bridge samples, considering the nonlinear behaviour of critical bridge components. When the seismic hazard in the site is controlled by a few seismic sources, it is important to quantify separately the contribution of each fault to the structure vulnerability. In this study, seismic records come from earthquakes that originated in strike-slip and reverse faulting mechanisms. The influence of the earthquake mechanism on the seismic vulnerability of the bridges was analysed by considering the displacement ductility of the piers. An in-depth parametric study was conducted to evaluate the sensitivity of the bridges' seismic responses to variations of structural parameters. The analysis showed that uncertainties related to the presence of lap splices in columns and superstructure type in terms of integral or simply supported spans should be considered in the fragility analysis of the bridge system. Finally, the fragility curves determine the conditional probabilities that a specific structural demand will reach or exceed the structural capacity by considering peak ground acceleration (PGA) and acceleration spectrum intensity (ASI). The results also show that the simply supported bridges perform consistently better from a seismic perspective than integral bridges and focal mechanism of the earthquakes plays an important role in the seismic fragility analysis of highway bridges.